JPH09207364A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the formation of unnecessary printing on thermosensible recording medium by allowing heat in a glass substrate to be conduction absorbed excellently into the radiation plate side to thus avoid the temperature of the glass substrate from being heated redundantly. SOLUTION: The thermal head is comprised by placing and fixing a glass substrate 1 with a plurality of heat resistors 2 coated to be arranged on its upper surface on a radiation plate 5, and a recessed groove 1a is made on a lower surface of the glass substrate 1 in the region underneath the heat resistors 2, furthermore, a heat good conductor 4 having a larger coefficient of heat conduction than that of the glass substrate is buried in the recessed groove 1a. In addition, the heat good conductor 4 is formed with a lead wire having a diameter being substantially equal to the depth of the recessed groove 1a provided on the lower surface of the glass substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a thermal head incorporated as a printer mechanism such as a word processor and a facsimile.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a thermal head incorporated as a printer mechanism such as a word processor has a plurality of heating resistors 12 on its upper surface and each heating resistor 1.
2 has a structure in which a substrate 11 provided with a pair of electrodes 13 connected to both ends of 2 is placed and fixed on a heat dissipation plate 14 made of a material having good thermal conductivity such as aluminum using double-sided tape or the like. A predetermined electric power is applied between the pair of electrodes 13 to cause the heating resistor 12 to selectively generate Joule heat based on a print signal from the outside, and the generated heat is transferred onto the heating resistor 12. To the thermal recording medium,
It functions as a thermal head by forming a predetermined print image on the thermal recording medium.

Recently, as a substrate material for such a thermal head, a thin glass plate (having a thickness of about 1 mm) which is inexpensive and has excellent flatness has been attracting attention. By applying this thin glass plate as the substrate 11 of the thermal head, By pressing each heating resistor 12 on the substrate 11 against the thermosensitive recording medium with substantially uniform strength, a good printed image can be formed and the thermal head can be manufactured at a relatively low cost. Become.

[0004]

However, in this conventional thermal head, when the substrate 11 is made of thin glass, the thermal conductivity of the substrate 11 is about 0.9 W.
/ M · k, which is relatively small, the substrate 11
Heat easily accumulates inside the substrate 11 when printing is repeated.
It is impossible to properly conduct the internal heat to the heat dissipation plate 14 side, and the substrate 11 becomes excessively high in temperature. As a result, unnecessary printing is formed on the heat-sensitive recording medium, so-called trailing phenomenon occurs. Had.

[0005]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and is a thermal head comprising a glass plate having a plurality of heating resistors adhered on the upper surface thereof and mounted on a heat dissipation plate. In the lower surface of the glass substrate, a groove is provided in a region directly below the heating resistor, and a good thermal conductor having a larger thermal conductivity than that of the glass substrate is embedded in the groove. To do.

Further, the thermal head of the present invention is characterized in that the good thermal conductor comprises a conductive wire having a diameter substantially equal to the depth of the concave groove provided on the lower surface of the glass substrate.

[0007]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a thermal head of the present invention, FIG. 2 is a sectional view taken along line XX of FIG.
Reference numeral a is a groove, 2 is a heating resistor, 4 is a good thermal conductor, and 5 is a heat radiating plate.

A thin glass sheet having a thickness of about 1 mm is used as the substrate 1, and has a thermal conductivity of about 0.9, for example.
It is manufactured by forming a low-alkali glass having a W / m · k and a softening point of 700 to 800 ° C. into a plate shape and polishing the surface.

On the upper surface of the substrate 1, a plurality of heating resistors 2 arranged in a straight line and a pair of electrodes 3 connected to both ends of each heating resistor 2 are sequentially deposited. .

The heating resistor 2 is made of tantalum nitride or the like and has a predetermined electric resistivity, so that when an electric power is applied from an external power source through the pair of electrodes 3, the joule is heated. A predetermined temperature required to generate heat and form a printed image on a thermosensitive recording medium, for example 200 to 350 ° C
The effect of generating heat at the temperature of.

The pair of electrodes 3 are made of a metal such as aluminum and serve to apply electric power from an external power source to the heating resistor 2.

The heating resistor 2 and the pair of electrodes 3 are formed in a predetermined pattern on the substrate 1 by employing the conventionally known sputtering method and photolithography technique.
It is applied to a predetermined thickness.

On the other hand, on the lower surface of the substrate 1, a groove 1a is provided in a region directly below the heating resistor 2, and the thermal conductivity (for example, 1.0) larger than that of the substrate 1 is provided in the groove 1a.
A good thermal conductor 4 having a W / m · k or more) is buried.

The recessed groove 1a is for reducing the thickness of the substrate 1 located immediately below the heat generating resistor 2 and for embedding the good thermal conductor 4 therein. It has a size of 0.9 mm and a width of 0.3 to 1.0 mm, and is formed in a strip shape substantially parallel to the array of the heating resistors 2.

Further, the good thermal conductor 4 embedded in the concave groove 1a of the substrate 1 is for conducting the heat in the substrate 1 favorably to the heat dissipation plate 5 in a short time.
For example, the conductive wire 4a (heat conductivity:
393 W / mk) and a heat dissipation grease 4b made by adding inorganic filler such as alumina to silicone grease
(Thermal conductivity: about 1.0 W / m · k) is used together.

As described above, the predetermined groove 1a is provided on the lower surface of the substrate 1 immediately below the heating resistor 2, and the good thermal conductor 4 having a higher thermal conductivity than the substrate 1 is provided in the groove 1a. Since it is embedded, the heat in the substrate 1 is satisfactorily conducted to the heat dissipation plate 5 side through the good thermal conductor 4 in the groove 1a in a short time, and even when printing is repeated, It is possible to effectively prevent the substrate 1 from reaching an excessively high temperature. As a result, the substrate 1 is kept at a temperature suitable for printing, and it becomes possible to always form a clear and good predetermined printed image on the thermosensitive recording medium.

At this time, if the diameter of the conductor wire 4a is made substantially equal to the depth of the groove 1a, the conductor wire 4a is brought into contact with both the bottom surface of the groove 1a and the top surface of the heat dissipation plate 5. Therefore, it is possible to increase the mechanical strength of the substrate 1 by supporting the substrate 1 on the heat dissipation plate 5 via the conductive wire 4a at the bottom surface of the concave groove 1a. Therefore, during printing, even if the thermal recording medium is pressed against the substrate 1 with a predetermined pressing force, the substrate 1 does not easily crack due to the pressing force. Therefore, it is preferable to make the diameter of the conductor wire 4a substantially equal to the depth of the groove 1a. At this time, as the conductive wire 4a, a metal material having a Brinell hardness of 20 H _B or more (for example,
Copper, iron, aluminum, etc.) is used. The groove 1a
Is formed at a predetermined position on the lower surface of the substrate with a diamond blade so as to have a depth of, for example, 0.6 mm, and then the conductor wire 4a and the heat radiating grease 4b are embedded in the concave groove 1a.

Further, such a substrate 1 is placed on the upper surface of a heat dissipation plate 5 made of a material having good heat conductivity such as aluminum via an adhesive member such as a double-sided tape.
Fixed to

The heat radiating plate 5 is for supporting the substrate 1 on its upper surface, and is manufactured by forming an ingot (lump) of aluminum or the like into a predetermined shape by a conventionally known metal working method, for example. The thermal head as a product is completed by fixing the substrate 1 on which the heat generating resistor 2 and the like are adhered on the heat dissipation plate 5 by using a double-sided tape or the like.

Thus, the above-mentioned thermal head applies a predetermined electric power between the pair of electrodes 3 to selectively cause the heating resistor 2 to generate Joule heat based on the print signal.
The generated heat is conducted to the thermosensitive recording medium to form a predetermined printed image on the thermosensitive recording medium, thereby functioning as a thermal head.

The present invention is not limited to the above-described embodiment, but various modifications and improvements can be made without departing from the gist of the present invention. Although both the conductive wire 4a and the heat dissipation grease 4b were used, instead of this, as shown in FIG. 3 (a), the conductive wire 4a was used alone as the good thermal conductor 4, and the conductive wire 4a and the substrate groove 1a The gap may be filled with the same glass as the material of the substrate 1, or as shown in FIG.
As shown in (b), the conductive wire 4a may be coated with a material having good solder wetting property such as nickel and gold, and this may be soldered to a predetermined portion of the heat dissipation plate 5 (4c is soldered). At this time, the thermal conductivity of the solder 4c is 42 W / m · k and the thermal conductivity of the glass forming the substrate 1 (0.9 W / m · k).
Since it is sufficiently larger than k), the heat conduction from the conductive wire 4a to the heat dissipation plate 5 is even better than that of the above-described embodiment.

In addition to this, as shown in FIG. 3C, for example, as the good thermal conductor 4, a heat dissipation grease, a metal material such as solder, nickel plating, copper plating, or alumina is used alone, or As shown in FIG. 3 (d), a convex portion 5 a is provided on the upper surface of the heat dissipation plate 5 made of aluminum (heat conductivity: 130 to 200 W / m · k) or the like, and the convex portion 5 a is part of the good thermal conductor 4. As a result, it may be inserted into the concave groove 1a of the substrate 1 and the gap between the both may be filled with the heat radiating grease 4b or the like, and these modified examples also have the same effect as the above embodiment.

Particularly in the example of FIG. 3C, the good thermal conductor 4
When plating is formed by plating, since a large number of bubbles are present in the plating film and the density is lowered, when the thermal head is operated, a relatively large amount is present between the substrate 1 and the good thermal conductor 4. Even if a thermal stress is applied, the bubbles in the plating film are deformed to absorb and relax the thermal stress, and the substrate 1
Can be effectively prevented from being destroyed by thermal stress.

In the example of FIG. 3C, the good thermal conductor 4
When solder is used as the solder, copper plating, nickel plating or the like having good solder wettability is formed on the inner wall of the groove 1a by 0.1 to 0.5.
If the solder is deposited to a thickness of μm, when the solder is melted and poured into the concave groove 1a of the substrate 1, the solder is relatively easily filled in the concave groove 1a and the inner wall of the concave groove 1a is covered. The deposited plating film of nickel or the like can absorb and relax the thermal stress generated when the thermal head is operated.

[0026]

In the thermal head of the present invention, a groove is provided on the lower surface of the glass substrate immediately below the heating resistor, and a good thermal conductor having a higher thermal conductivity than that of the glass substrate is provided in the groove. Since it is embedded, the heat in the glass substrate can be satisfactorily conducted to the heat radiating plate side in a short time through the good heat conductor in the groove, and even when printing is repeated, the glass It is possible to effectively prevent the substrate from becoming excessively high in temperature. As a result, the glass substrate is kept at a temperature suitable for printing, and it becomes possible to always form a clear and good predetermined printed image on the thermal recording medium.

In the thermal head of the present invention,
By using a conductive wire having a diameter substantially equal to the depth of the groove as the good thermal conductor, the glass substrate can be supported on the heat dissipation plate via the wire at the bottom surface of the groove to enhance the mechanical strength of the glass substrate. . Therefore, at the time of printing, even if the thermal recording medium is pressed against the glass substrate with a predetermined pressing force,
The glass substrate does not easily crack due to the pressing force.

[Brief description of drawings]

FIG. 1 is a perspective view showing a thermal head of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

3A to 3D are enlarged cross-sectional views of a main part showing a modified example of the present invention.

FIG. 4 is a sectional view of a conventional thermal head.

[Explanation of symbols]

 1 --- Substrate 1a-Recessed groove 2--Heating resistor 3--Pair of electrodes 4--Good thermal conductor 4a-・ Wire 5 ・ ・ ・ ・ ・ ・ Heat sink

Claims (2)

[Claims] 1. A thermal head comprising a glass substrate having an upper surface on which a plurality of heating resistors are adhered and placed on a heat dissipation plate, the lower surface of the glass substrate being located directly below the heating resistors. A thermal head, characterized in that a groove is provided and a good thermal conductor having a thermal conductivity higher than that of the glass substrate is embedded in the groove. 2. The thermal head according to claim 1, wherein the good thermal conductor comprises a conductive wire having a diameter substantially equal to the depth of the groove provided on the lower surface of the glass substrate.